In Chicago today, teachers walked picket lines at more than 600 schools. It's the city's first teacher strike in 25 years. Over the weekend, negotiators failed to reach agreement on a contract. They're back at the bargaining table today in hopes of sending 350,000 students back to school before the public's patience wears thin.

From member station WBEZ in Chicago, Becky Vevea has the story.

BECKY VEVEA, BYLINE: Teachers outside Blaine Elementary School on Chicago's north side are decked out in red shirts today, carrying signs that read on strike.

PATRICK CLANCY: We're all showing up to our first picket. I can be honest and say we're all scared. We don't know what to expect.

VEVEA: Patrick Clancy teaches 7th and 8th grade math at Blaine and wants to get back to doing that.

CLANCY: Hopefully, this gets resolved within the week, I hope. We'll see. I want to get back to the classroom. This planning for a strike and planning for class and trying to mitigate the two, it's draining.

VEVEA: When talks ended late last night, union and district officials agreed they are close on compensation, but remain stuck on issues of job protection and teacher evaluation. Chicago Mayor Rahm Emanuel says the union quit too early last night.

MAYOR RAHM EMANUEL: This is not a strike I wanted. It was a strike of choice that is totally unnecessary.

VEVEA: But Emanuel is standing firm on issues of job protection. He says neither the school district nor the union should tell principals which teachers they can and cannot hire. Emanuel and the Chicago Teachers Union have butted heads ever since he took office. The former White House chief of staff wants to shake up the public schools by lengthening the school day and year, changing how teachers are evaluated and paid, and expanding privately run charter schools.

Many of those reforms mirror those being pushed across the country and are central to President Barack Obama's education agenda. In Chicago, the union sees its contract fight as a larger battle to push back against what it says is the privatization of public schools across the country. Teachers picketing Monday also say the strike could be bad for President Obama's reelection campaign, even though labor unions have long been part of the Democratic base. Again, teacher Patrick Clancy.

CLANCY: This anger with the mayor right now is going to translate into a - it could turn into a loss of votes for the president. I mean, I don't know. I mean, I don't want to speak for anybody else, but I know that's crossed my mind.

VEVEA: Apparently, it's crossed some other minds, too. Within hours of picket lines starting, Republican presidential candidate Mitt Romney pounced on the opportunity to criticize unions and President Obama for siding with them. The president has not commented on the strike today. For parents in Chicago, the strike is a local issue and one they hope won't get dragged out.

Wendy Katten heads the parent group called Raise Your Hand and says she's already fielded a few angry emails from parents who want their kids to be in school.

WENDY KATTEN: Parents, I think, it will be OK if we have a short strike. We'll get through. But I really think it could be damaging to relationships if this is a long strike.

VEVEA: Abbie Kelly has two children in public school and is hopeful.

ABBIE KELLY: It sounded like they were pretty close and there's just a - you know, we've made some progress in some areas. So I was encouraged that if we can make some progress in some areas, we should be able to make it in others.

VEVEA: In the meantime, she'll spend some quality time with her daughters.

KELLY: We were thinking about the aquarium today.

UNIDENTIFIED CHILD: Yeah.

KELLY: Yeah.

UNIDENTIFIED CHILD: And Dunkin' Donuts.

KELLY: And Dunkin' Donuts, yes. We're going to Dunkin' Donuts.

VEVEA: For many of the 350,000 children in Chicago, today was a surprise. Depending on negotiations, tomorrow may be, too. For NPR News, I'm Becky Vevea in Chicago. Transcript provided by NPR, Copyright National Public Radio.